Control circuit



1943. A. A. MACDONALD 7 CONTROL CIRCUIT Filed April 19, 1945- i 23 9 mg /8 wnuzssas: INVENTOR ATTQRNE Patented Dec. 21, 1948 UNlTZED S TATES -GFHCE CONTROL CIRCUIT Angus AJMacdonald; Catonsville,- Mi, :assignorto Westinghouse Electricrcorporation,East rRittsliurgh la a corporation of Pennsylvania I ApplicationApril 19, 1945,--Sei'ial No.- 5895253 6 Claims. (Cl. -25027) My invention relates to electric control circuits -and, in particular, *relates to circuits in which it is desired to cause impression on the input" circuit of pulses havinga duration-which is short compared with'theperiodic time separating them to produce on the output terminals a voltage -which-pulsates only slightly. Suchan arrangementwould be useful, for example, in causing input'voltagepulsesof the type described to close or open an electromagnetic relay in the output circuit.

ne object of -my invention is, accordinglmto provide a circuitin which periodic voltage pulses having a -duration small compared with the in- :terval separating them producean output voltage Which fluctuates only slightly.

.iAnother-object of my invention is to produce an arrangement in which substantially squaretoppedvoltage "pulseshaving a width small compared with the-periodic time separating them will i'produce output voltages which fluctuate only slight y.

Still'another objector my-invention is to protduce-a circuit for enabling voltage pulses, having azdurationshort compared with the periodic time separating'them, toefiectively operate an electromagnetic: relay.

Still another-object of my invention'is' to provide acir'cuit inwhich voltages having relatively peakedhwaveforms shall-produce output currents :plaining the op'eration'of the circuitof Fig; 1.

w-Refenringin detail to Figure 1, my circuit em-.

bodies a pair of input-terminals u zadapted to impress voltage" througha capacitor 3' and aresister 4 on the control electrode?) of'an electron tube-6. Cooperating with thecontr'ol electrode 5 ca thode l connected-t0 the input'terminal 2 andto groundand anode Sconnect-ed through a resisto1-9 to' the positive "terminal I l' of a voltage source (not shown); the negative terminal 1.Of

whichds connected to terminal 2. :Thetanode1 '&

is likewiseconnectedsthroughm pair of -resistors 12, 13 ztO theinegati-ve' terminal ofz azisuitablevvoltage sourcesinot: shown):,-of which the positive terminallis wconnectedztoxthes terminal i. The zoommon terminal OfilJhBIIESiStOTS 1'2 and i3 isxconnectedto a second controlelectrode' liLwhichrcontrols -::currentafiow*zbetween 5a cathode .155 vand an anode :IG. Ihencathode fill-S connected torthe terminal dzand' the anedeitt is :conneetedwthrough a resistorpll and? the energizing windingiof Ea, relay 118 to the:positive:;terminal 19 ot in voltage source: having itsz'negative terminal connected to terminal i=2. A 'ca'pacitornlf-l iisrconnectecl :between the anode l6iandi-thetcontrol electrode-11:4. The relay I 8 is mdapted rim control z-current :fiow, tin ways well-known to 'those z'skilledzinathe tart, throughrany. desired-conceit:tconm'ectedctor the terminals 22,43.

Tihe circuit: nix-Fig.1iiisparticulajrly nseful .when voltage, pulses of' a duration rrelativelysshortuoompared to the: time interval separating: them, such. for exa'mple, =as 'Ith0se.;indioated zbynthe murve "e1 in 2, impressedon the terminals l,$-2. tWhen no 'such voltage pulses arerbeingrimpressed, the potential :of the Lcontrol" electrode 5 is substantially that of the cathode I'Ivand the structure of thextube o. isvssucha thatmnderlsuch-conditions, a substantial :current will :iflow from, positive :terminal H through resistor *9,- anodei-a and cathode 'l. The resistors;19, -t2 and .137 have a highwalue compared with the -intemalzimpedance -1 between the anode- 8 an dwcathoderil',underysuchcconditions, and; inconsequence;rthezianode 'ra is very nearly at the potential aof terniinal l :T-he resistors I12 and: t3 arelsoiproporticnedthat; under the conditions' just-mentioned;itheccontrol'electrode I 4 I'iS= so negative relative to cathode l5 that-substantially no current fiows :through melay 1&8, resistor l'l, anodelfixand cathode I 5. iThe-relayzlaisconseduently deenergized.

. If nowtvoltage pulses of ,lthewformer in :Fig. 2 are 'impresssed ontthel terminals 1 ,12, they I will charge the capacitord :inxsuch'ga sense (that its terminal-adjacent the *OOIltIOleBlGCtI'OdG :5 .is negative relative' 'tol the terminalll. 'As-soon as the voltage pulse ll-impressed :on terminals I, 52 falls from? @its peak 1' tocitst-trough :value, c as indicated in Fig. 2, the voltage impressedlbyucapacitOrB on controL electrode 5-wil1 lbecomernega-tive. 'By giving the. resistornl a sufliciently high value, it maybe arrangeclithatwthe charge ,thusr'existing on capacitor-.3 shall rdissipate with relative slowness compared withzth'ekperiodiczrtime "between successivexpulsesiofi voltage :Le1. lIn :consequence, the voitageximpzesced whetween the scatlmde :1

and control electrode will have the wave form indicated by the curve e: in Fig. 2. This voltage constitutes a negative bias for the control electrode 5 during the relatively long periods separating successive pulses of voltage e1. The value of the pulses er and the above-described circuit connected thereto are so designed that the negative bias represented by the long trough period of voltage e: is suflicient to cut on current flow from the anode 8 to the cathode I. As a result of this, the voltage of anode 8, which has the Wave-form marked ea, assumes a value determined by the relative magnitudes of the resistors 9, I2 and I3 and these resistors are so proportioned, in ways obvious to those skilled in the art, that the control electrode ll becomes sumciently positive so that current flows readily between the anode l6 and the cathode i5. Current can thus flow from the positive terminal 19 through the winding of relay i8 and resistor IT to energize and actuate the relay I8. The potential impressed between the anode 8 and terminal 2 is of the character indicated by the curve e: in Fig? '2, and comprises long positive voltage crests separated from each other by relatively short troughs which are simultaneous with the positive pulses oi! the impressed voltage ei. The capacitor 2| is given such a value as to act in conjunction with resistor l1 and relay winding ii to filter out the short voltage fluctuations which the troughs oi voltage ea would otherwise produce in the current flowing from positive terminal I8 through relay l8. The voltage drop across the resistor I1 is, accordingly, nearly devoid of fluctuations and may be applied to any desired output circuit at will.

It will be noted that the connection of the capacitor 2| between the control electrode l4 and anode l6 provides a very efllcient filtering action due to the amplifying efi'ect of the grid and plate action of electrodes I4 and I6. In other words,

when the control electrode l4 tends to become more positive, the plate l6 tends to become negative by an amount equal to the voltage amplification of the electrode system l5, ll, I6.

I claim as my invention:

1. In combination with a source of voltage pulses which are of short duration compared with the periods separating them, a pair of output electrodes and a control electrode, means for impressing said voltage pulses through a capacitor between said control electrode and one of said principal electrodes, a source of substantially constant voltage connected to said principal electrodes through an impedance, means for impressing a voltage derived from the potential difference between said principal electrodes on an input circuit, a tube comprising an anode, a cathode and a control electrode cooperating with them, means for impressing the last-mentioned voltage to control current flow between said anode and cathode, an impedance supplied with current from a constantvoltage source through said anode and cathode, means for energizing a work circuit by currentfiowln'g:

through the last-mentioned impedance, and a trode, a resistor fed through said principal electrodes from a source of substantially constant voltage, means for impressing fluctuations in voltage between said principal electrodes on a second control electrode, a second pair of principal electrodes associated with said second control electrode, a load circuit connecting a second source of substantially constant voltage to said second pair of principal electrodes and a capacitor connected between said second control electrode and a point on said load circuit.

3. In combination with a source of fluctuating voltage having voltage pulses which are short compared with the time periods separating them, a capacitor and a resistance serially connected across said source, a pair of principal electrodes connected to a source of substantially constant voltage through a resistor, a control electrode associated with said principal electrodes and connected to the common junction of said capacitor and first-mentioned resistance, resistance means in series with a source of bias voltage across said principal electrodes, a second pair of principal electrodes connected in series with a work circuit to a source of constant voltage, a control electrode associated with said second pair of principal electrodes connected to a point on the last-mentioned resistance and a capacitance connected between the last-mentioned control electrode and a point on said work circuit.

4. In combination with a source of voltage pulses which are of short duration compared with the periods separating them, a pair of output electrodes and a control electrode, means for impressing said voltage pulses through a capacitor between said control electrode and one of said principal electrodes, a source of substantially constant voltage connected to said principal electrodes through an impedance, means for impressing a voltage derived from the potential difference between said principal electrodes on an input circuit, a tube comprising a cathode, an anode, and a control electrode cooperating with them, means for impressing the last-mentioned voltage to control current flow between the lastmentioned cathode and anode, an impedance supplied with current from a constant voltage source through the last-mentioned cathode and anode, means for energizing a Work circuit by current flowing through the last-mentioned impedance, and a capacitor connected between the last-mentioned control electrode and said anode.

5. In combination with an input circuit for impressing voltage pulses which are short compared with the time periods separating them, a first pair of principal electrodes and a control electrode associated with them, means for impressing said voltage pulses through a capacitor in series with resistor on said control electrode, a resistor fed through said principal electrodes from a source of substantially constant voltage, means for impressing fluctuations in Voltage between said principal electrodes on a second control electrode, an anode and cathode associated with said second control electrode, a load circuit connecting a second source of substantially constant voltage to said anode and cathode and a capacitor connected between said second control electrode and said anode.

6. In combination with a source of fluctuating voltage having voltage pulses which are short compared with the time periods separating them, a capacitor and a resistance serially connected across said source, a pair of principal electrodes ccmie icd $0 a source of substantially constant 5 voltage through a resistor, a control electrode capacitance connected between the last-menassociated with said principal electrodes and connned control electrode and said anode.

nected to the common junction of said capacitor ANGUS MACDONAID- and first-mentioned resistance, resistance means in series with a source of bias voltage across said 5 REFERENCES CITED principal electrodes, an anode and cathode con- The f11W1n8 references are of record in the nected in series with a work circuit to a source me of this patent of constant voltage, a control electrode associated UNITED STATES PATENTS with said anode and cathode connected to a 10 Number Name Date point on the last-mentioned resistance and a 2,147,781 Ward Feb. 21, 1939 

